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What is McArdle disease?
McArdle disease (glycogen storage disease type V) is an autosomal recessive disorder caused by deficiency of myophosphorylase, the enzyme responsible for liberating glucose molecules from glycogen in skeletal muscle.
Patients present with a lifelong history of poor exercise tolerance, and minimal physical exertion may cause muscle pain, muscle contractures, and rhabdomyolysis.
Muscle contractures are described as muscles “locking up.”
During a muscle contracture, the muscle is electrically silent, and, unlike common neural cramps, cannot be improved with stretching or massage.
Another characteristic feature of McArdle disease is the “second wind” phenomenon, where patients experience improved exercise capacity after briefly resting after initiating exercise.
This phenomenon is attributed to muscle metabolism of fatty acids or extramuscular-derived glucose.
How is McArdle disease treated?
Patients should be counseled to avoid high intensity exercise.
Additionally, moderate, regular endurance exercise has been shown to improve exercise tolerance.
Sources
- Amburgey K, Bailey A, Hwang JH et al.: Genotype-phenotype correlations in recessive RYR1-related myopathies. Orphanet J Rare Dis 8: 117, 2013.
- Snoeck M, Engelen GMV, Kusters B et al.: RYR1-related myopathies: a wide spectrum of phenotypes throughout life. Eur J Neurol 22:1094-112, 2015.
- Bembi B, Cerinin E, Danesino C et al.: Diagnosis of glycogenosis type II; review. Neurology 2: (23 Suppl 2):S4-S11, 2008.
- Katzin LW, Amato AA: Pompe disease: A review of the current diagnosis and treatment recommendations in the era of enzyme replacement therapy. J Clin Neuromuscul Dis 9:421-431, 2008.
- Kishani PS, Corzo D, Nicolino M et al.: Recombinant human acid [alpha]-glucosidase: major clinical benefits in infantile-onset Pompe disease. Neurology 68:88-89, 2007.
- Slonim AE, Bulone L, Goldberg T et al.: Modification of the natural history of adult-onset acid maltase deficiency by nutrition and exercise therapy. Muscle Nerve 35:70-77, 2007.
- Auinlivan R, Beynon RJ, Martinuzzi A: Pharmacological and nutritional treatment for McArdle disease. Cochrane Database Sys Rev 6:CD003458, 2008.
